Alkylation



Patented May 20, 1941 ALKYLA'rIoN Arthur L. Blount, Palos Verdes Estates, Calif.,l

assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California i Application August 14, 1939, Serial No. 290,002

.6 Claims.A

This invention relates to a method of producing alkylated hydrocarbons. More specifically this invention is for the production of saturated side chain parafnic hydr`carbons by reacting olens with isop-arafns in the presence of a catalyst, such as strong sulphuric acid. These saturated side chain parainic hydrocarbons possess highly anti-detonating characteristics and are, therefore, valuable as constituents of motor fuel for internal combustion engines.

When one or more molecules of an olen react with an isoparailinic hydrocarbon an alkylated parafnic hydrocarbon is produced which possesses a side chain and is saturated. This reaction between an olefin and an isoparain is, therefore, different from the reaction which takes place by the interaction between two olefin molecules which produces a polymerized hydrocar-A bon or a polymer.

The reaction between olefms and isoparans to lform alkylated hydrocarbons may be promoted by such catalysts as aluminum chloride, chlorsulphonic acid or concentrated sulphuric acid. The present invention employs sulphuric acid as the catalyst. When I employ my process to produce the maximum yield of alkylated hydrocarbon on the basis of the aci-d I continuously use the acid until it has an apparent H2804 concentration of 80% (actually 91.0% H2804) at which concentration the acid is no longer an efficient -alkylation catalyst. In other Words, I may initiate the reaction between the olefins and the isoparans with sulphuric acid having an actual H2804 concentration between 98% and 103% and continue the use of this acid for further alkylation of olens and isoparains until it has degraded to an apparent concentration of 80% H2804. During the continued use of the sulphuric acid it dissolves a certain portion of hydrocarbon materials. When the acid phase with its dissolved material shows by analysis on the weight basis an 80% H2804 content it is of little value as an alkylation catalyst. If this acid 'hav.

ing an apparent concentration of 80% is separated from its hydrocarbon content i-t will be found to possess an actual H2804 concentration of about 91%. Therefore, when I refer to apparent acid concentrations in this specification I mean the H2804 concentration of the acid containing dissolved hydrocarbons.

When I employ my process to produce the maximum amount of alkylated product on the olefin basis, the acid should not be permitted to reach an apparent H2804 content substantially lower than 88.0% and preferably it should be employed between the apparent concentrations of 95% H2804 to 88% H2804. Furthermore, the optimum concentration of acid to employ to obtain the maximum yield of alkylated hydrocarbon on the olefin basis is about 91% apparent H2804 concentration which corresponds to an actual H2804 concentrationv of 96%. I, therefore, may

` initiate the reaction between the olefin and isoparailinic feed stocks with 98% to 103% H2804 and as the H2804 concentration degrades through continued use I may fortify this acid with the addition of more concentrated sulphuric acid (as for example 98% to 103% H2804) to maintain the strength of this acid between an app-arent concen- -tration range from 95.0% H2804 to 88% H2804 and preferably around an apparent concentration of 91% H2804. Instead of fortifying the parti-ally spent acid withmore concentrated sulphuric acid I may obtain the same result by contacting the partially spent sulphuric acidwith sulphur trioxide.- By withdrawing the partially spent acid from the alkylation zone and countercurrently contacting this acid with sulphur ltrioxide the strength of the acid may be maintained within the optimum apparent .concentration range of from 95% to 88% H2804 and preferably around an apparent H2804 content of 91%.

In carrying out the reaction between the olens and the isoparafiins in the presence of the catalyst to produce the alkylated product it is desirable to maintain a high ratio of isoparaffin to olefin, This high ratio of isoparaftin to olefin `favors alkylation and minimizes polymerization.

This ratio should be in the order of at least five parts of isoparailin to one part of the olei'ln and preferably ten parts to fifty parts of the isoparaflin to one part of the olefin. Furthermore, sucient pressure should be imposed on the olens and isoparafns to maintain these hydrocarbons in a liquid state during contact with the sulphuric acid. l

When isobutane is alkylated with butylene in the presence of sulphuric acid the optimum temperatures to be employed lie between 30 F. and 60 F. and preferably around 45 F. Furthermore, when propylene is alkylated with isobutane in the presence of sulphuric acid the optimumtimum temperature as Well as .the optimum temperature range may be determined for the alkylation of isobutane with -any mixture of propylene and butylene in the presence of sulphuric acid having an H2804 content between an initial actual 103.5% to an apparent 80.0%. When I use the term propylene or butylene I mean either the gaseous olens or 4the polymers of either propylene or butylene, since either mixtures of gaseous propylene and butylene or mixtures of polymerized propylene and butylene may be usedfin my process. Furthermore, gaseous propylene or butylene may be mixed with polymerized propylene or butylene and the resulting mixture em ployed in my process.

My invention will be better understood from 5 a study of the accompanying drawing.

The gure shows a series of curves which represent the yield of alkylated hydrocarbons on the olen basis produced at various temperatures by alkylatingbutylenes with isobutane, propylene with isobutane andv mixtures of propylene and butylenes with isobutane using sulphuric acid of 98% H2SO4 initial concentration in each case as the catalyst.

Referring to the drawing, it will be noted that the optimum temperature for alkylating a mixture containing propylene and 80% butylene with isobutane in the presence of sulphuric acidl is 54 F. The optimum range of temperature for this mixture is' in the order of 45 F. to 65 F. 20 For the alkylationof an olen mixture containing 40% propylene and 60% butylene with isobutane in the presence of concentrated sulphuric acid the optimum temperature is about 61 F. and the optimum temperature range is 25 between 50 F. and '10 F.' 'For the alkylation of an oleiin mixture containing 80% propylene and 20% butylene with isobutane in the presencer of 98% H2S04, the optimum temperature is about 67 F. and the optimum temperature range 30 between 60 F.and 80 F.

I find that the optimum temperature at which the maximum yield of product can' be obtained fromjthe alkylation of'propylene-butylene mix-f.

tures or solutions of these olens in inert hydro- 35 carbons, using isobutane as the other reactant and using 98% sulphuricacid as the catalyst until it has degraded to an apparent 80% by weight H2804 may be determined by the following equation:l

Where Y=temperature of maximum yield in F. and

X=propylene content "of the olen feed stock* lexpressed as A% by .volume of the propylene -plus butylene' in the feed.

From the above it is clear that in a mixture consisting of 50% inert hydrocarbons, 25% 50 propylene and 25% butylene, X would equal 50%.

By reference to the curves it is also apparent that the optimum temperature range within which the maximum yield of alkylated product can be obtained from the alkylation of propylenebutylene mixtures or solutions of these olefins in inert hydrocarbons using isobutane as the. other reactant and using sulphuric acid between the concentrations of 98% andan apparent 80% by weight H2804 may be expressed as lying between Y=0.25 x+4o and Y=0.25 x+55 where Y equals temperature of maximumyield in vF. and X equals propylene content ci the 65 olefin kfeed stock expressed in percent by volume of the propylene plusbutylenes in the feed.

As explained above, if reference is made tothe drawing, it will be noted that a maximum yield of alkylated hydrocarbon is obtained (on the olefin basis) at about 54 F. if an olefin mix ture containing 20% propylene and 80% butylene is reacted with isobutane in the presence of H2504 between an actual H2804 content 'pf l' 98% and an apparent concentration -of 80% 75 A (both H2804 concentrations calculated on a weight basis).

Applying the above data to the formula:

stantially at a temperature determined by the equation where Y is the temperature in F. to be employed and X represents vthe propylene content expressed as percent by volumeof the propylene plus butylene in the olen mixture.

2. In a process of reactingI an olen mixture containing propylene and butylene with isobutane in the presence of concentrated sulphuric Y. acid comprising conducting thereaction within the temperature range determined by the expressions Y=0.25 x+4o and Y=0.25 x+55 Where Y is the temperature in F. to be employed and X represents the. propylene content expressed asA percent by volume of the propylene plus butylene in said olefin mixture.

3. A process for the production of alkylated hydrocarbons' which comprises commingling an olefin mixture containing propylene and butylene with isobutane and with sulphuric acidv at a temperature determined by the expression Y where Y represents the temperature in F. to be employed and X represents the propylene content expressed as percent by volume of the propylene plus butylene in said olen mixture.

4. A process as claimed in claim 1 in which4 the concentration of the sulphuric acid employed liesvbetween an actual 98.0% H2804 by weight and an apparent 80% H2804 by weight. 5. A process as claimed in claim 2 in whic the concentration of the sulphuric acid employed lies within the limits of 98.0% H2804 by weight and an apparent HzSO4 by weight.

6. A process for the production of alkylated hydrocarbons which comprises contacting isobutane and an olen mixture containing propylenel and butylene with sulphuric .acid having an E804 content by weight between about 98% and 92% and maintaining a temperature during said contact within the limits determined by the expressions Y=0.25 X+40 and Y=0.25` X+50 where Yrepresents the temperature in F. and X represents the propylene content expressed as percent by volume ofthe propylene plus 

